Why are my particles getting cut off the top and bottom of my render?
Following my comment, considering the context (new to Blender, etc.), here is some more information.

The rendered scene parts (text and particles) are reworked using the 'compositor'. This compositor allows to tune how all this is mixed.

Here, it uses a box mask which is too small in its height (0.35).

To fix this, open another view. Set it to 'nodes editor' (1), then select the compositor (2), find the box mask and change its height (3).